1. Field of the Invention
The present invention relates to a structure for mounting a drive unit including an engine on a vehicle.
2. Description of Relevant Art
A proposed drive unit mounting structure suitable for use on a substantially small-sized three-wheeled vehicle having a front wheel and a pair of rear wheels is known. In this known vehicle a rear fork is pivotally supported on a rear portion of a vehicle body, a drive unit including an engine is mounted on the rear fork, and the rear wheels are drivably connected to the drive unit on respective opposite sides thereof. The drive unit as well as the rear wheels are not spring-mounted, and the weight thereof amounts to one-third to one-half of the entire weight of the vehicle. Further, the small-sized vehicle is not normally provided with a hydraulic damper in its cushioning system which provides sufficient dampening effects. Normally, a vibration-dampening structure is employed to reduce relatively fine vibrations of the drive unit between the drive unit, especially the engine, and the rear fork that supports the engine thereon. Such vibration-dampening structure tends to amplify a relative pivotal movement between the engine and the rear fork. When such a vehicle is in motion and is suddenly braked by applying a large braking force to the driven rear wheels, the vehicle tends to hop at the rear wheels. Such hopping is difficult to control or suppress because sufficient shock-dampening action is not provided, thus causing discomfort to the driver during vehicle operation in further view of the fact that the spring-supported weight of the vehicle is small in comparison with the weight thereof which is not spring-supported.